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The nucleotide sequences of the rDNA second internal transcribed spacer (ITS-2) of 31 populations of 12 and 3 species of the two main Triatominae tribes Triatomini and Rhodniini, including the most important Chagas disease vectors, were obtained. Sequence comparisons and parsimony, distance, and maximum-likelihood analyses indicate that ITS-2 is a useful marker for resolving supraspecific, specific, subspecific, and even sometimes population-level relationships in Triatominae. Results were markedly different between species of Triatomini and Rhodniini, suggesting polyphyly. Phylogenetic trees support an old divergence between South American and North–Central American Triatomini and query the validity of some genera (Dipetalogaster, Psammolestes). The very low sequence variation between species of the phyllosomacomplex suggests that subspecific ranking would be more appropriate. Triatoma dimidiataproves to be a clearly differentiated species, with several populations evidencing a clinal variation along a north–south axis and a population from Yucatan showing differences consistent with specific status.

Abderrazak, S. B., Oury, B, Lal, A. A., Bosseno, M.-F., Force-Barge, P., Dujardin, J.-P., Fandeur, T., Molez, J.-F., Kjellberg, F., Ayala, F. J., and Tibayrenc, M. 1999. Plasmodium falciparum: Population genetic analysis by multilocus enzyme electrophoresis and other molecular markers. Experimental Parasitology92, 232–238. The population structure of Plasmodium falciparum, the agent of malignant malaria, is uncertain. We have analyzed multilocus enzyme electrophoresis (MLEE) polymorphisms at 7–12 gene loci in each of four populations (two populations in Burkina Faso, one in Sudan, one in Congo), plus one “cosmopolitan” sample consisting of parasite cultures from 15 distant localities in four different continents. We have also performed random amplified polymorphic DNA analysis (RAPD) and restriction fragment length polymorphism (RFLP) and characterized gene varia tion at four antigen genes in the Congo population. All genetic assays show abundant genetic variability in all populations analyzed. With the isoenzyme assays, strong linkage disequilibrium is apparent in at least two local populations, the Congo population and one population from Burkina Faso, as well as in the cosmopolitan sample, and less definitely in the other Burkina Faso population. However, no linkage disequilibrium is detected in the Congo population with the molecular assays. We failed to detect any nonrandom association between the different kinds of genetic markers; that is, MLEE with RAPD or RFLP, RAPD with RFLP, and so on. Although isoenzyme data show statistical departures from panmictic expectations, these results suggest that in the areas under survey, P. falciparum populations do not undergo predominant clonal evolution and show no clear-cut subdivisions, un like Trypanosoma cruzi, Leishmania sp., and other major parasitic species. We discuss the epidemiological and taxonomical significance of these results.

Abstract: Pressure and flow were measured in the ascending aorta of eight anaesthetised dogs under control conditions, after volume expansion and after haemorrhage. For each case the characteristic impedance of the proximal aorta Zc was determined by means of two different methods. Zc was calculated in the time domain as the slope of the pressure-flow relationship in early ejection. For each case, six different values were also obtained in the frequency domain by averaging the impedance moduli in six different frequency ranges. Time- and frequency-domain values agreed well. Statistical analysis showed that both methods can be used to study changes in Zc. However, the time-domain method is easier to apply and does not require steady-state conditions.

RésuméQuatre espèces nouvelles de phlébotomes sont décrites. Trois espèces anthropophiles, Lutzomyia suapiensis, sp. n., L. tihuiliensis, sp. n. et L. tocaniensis, sp.n. sont décrites sur des femelles seulement ; elles sont apparentées à L. pia(Fairchild & Hertig) et, comme elle, appartiennent au sous-genre Pifanomyia, d'importance épidémiologique majeure dans les régions subandines. Une analyse morphométrique discriminante permet de séparer les différentes espèces et de les inclure dans le sous-genre Pifanomyia. Une quatrième espèce, Lutzomyia toroensis, sp. n., décrite d'après des spécimens mâles et femelles, est apparentée à L. oligodontaYoung et al.Ces deux espèces ne s'intègrent à aucun sous-genre ou groupe d'espèces de Lutzomyia; elles constituent un un "groupe naturel" de phlébotomes du sud-ouest de l'Amérique du Sud.

AbstractMale Lutzomyia longipalpisof two types from Bolivia were compared using isozyme electrophoresis and wing morphometry. One sample (exChiflonkaka Cave, alt. 2800 m at Toro Toro, Charcas Province, Potosi Department) was ‘two‐spot’ phenotype males (i.e. tergites III and IV with paired pale patches of pheromone glands), whereas two other locality samples (Apa Apa and Imanaco, Sud Yungas Province, La Paz Department) were one‐spot male phenotype (only tergite IV with paired pale patches). Multilocus enzyme electrophoresis (using ACON, aGPD, GPI, IDH, MDH, ME, 6PGD, PGM, LAP and PEPB) found no difference between samples from adjacent hen houses at Apa Apa. Nei's standard genetic distance between one‐spot samples from Apa Apa and Imanaco (5 km apart, 1500m alt.) was 0.001‐0.002, whereas the two‐spot males from Toro Toro (800 km away) showed a genetic distance of 0.081 from the one‐spot males (Apa Apa and Imanaco). This genetic distance is commensurate with speciation, but may simply be intraspecific differentiation due to ‘isolation by distance’.

Abstract: An electrical circuit which simulates a variable compliance is introduced and analysed. The circuit is simple, accurate and inexpensive. It can be used to demonstrate or study the physics of a nonlinear or time-variable compliance. Total arterial compliance is used as an example. Because of its simple structure, the circuit is also ideally suited to be implemented as a building block in a larger electrical model of the cardiovascular system.

Abstract: A 4-parameter model to represent the relationship between slowly changing arterial inflow and the resulting pressure change was proposed. In order to determine values for the parameters and test the model in a wide range of pressure and flow, two experimental procedures were used. Firstly, slow oscillations in aortic pressure (period, 4 sec) were produced by means of an external pump connected to the aorta, and secondly, cardiac arrest was induced for about 2–3 sec by stimulating the right vagus. It was shown mathematically that the pressure and pump displacement information obtained in these experiments could be related to the model parameters. Values for the model parameters were obtained in 6 anesthetized dogs using a least squares adjustment procedure. Using aX 2-test, it was concluded that the model represented the arterial system for each animal well.

Wing geometric morphometry of Triatoma infestans (Klug) (Hemiptera: Reduviidae) populations in northwestern Argentina showed that individual collection sites represent the discrete unit where metric differentiation took place. Here we studied temporal variations in wing size and shape of T. infestans populations from defined capture sites on three occasions between 2000 and 2003. Bugs collected from domiciles and/or storerooms had significantly larger right-wing centroid size than bugs collected at goat and/or pig corrals by the end of summer 2000 for both sexes. Conversely, male bugs collected from domiciles and/or storerooms had significantly smaller centroid size than bugs collected from pig corrals in spring 2002. The inversion in wing centroid size between seasons was consistent between sexes. Wing shape analysis from the south-central extreme of the study village showed divergence between collection dates for both sexes. Wing shape divergence was highly significant between male bugs collected by the end of summer 2000 and those collected in spring 2002 and by the end of summer 2003. For females, wing shape divergence was marginally significant between the end of summer 2000 and spring 2002, and significant between spring 2002 and the end of summer 2003. Unlike season-related variations in wing centroid size, shape differentiation was related to the time period elapsed between sample collections and suggested genetic influences acting on shape. Simultaneous consideration of wing size and shape provided complementary information on the direction and timing of bug dispersal. Morphological studies may allow determining the degree of relatedness of different bug populations and to associate morphological heterogeneity with temporal patterns of reinfestation.

The impact of landscape fragmentation due to human and climatic mediated factors on the structure of a population of Glossina palpalis gambiensis Vanderplank (Diptera: Glossinidae) was investigated in the Mouhoun river basin, Burkina Faso. Allele frequencies at five microsatellite loci, and metric properties based on 11 wing landmarks, were compared between four populations. The populations originated from the Mouhoun river and one of its tributaries. The average distance between samples was 72 km with the two most widely spaced populations being 216 km apart. The sampling points traversed an ecological cline in terms of rainfall and riverine forest ecotype, along a river enlarging from downstream to upstream and oriented south to north. Microsatellite DNA comparison demonstrated structuring between the populations, but not complete isolation, with an overall Fst = 0.012 (P < 0.001). Wing geometry revealed significant centroid size and shape differences between populations, especially between the two most distant populations. There was no significant correlation between gene flow and geographic distance at this scale, but there was a positive correlation in females between metric distances (wing shape differences) and geographic distances that might be attributed to the cline of environmental conditions. The impact of the fragmentation of riparian landscapes on tsetse population structure is discussed in the context of control campaigns currently promoted by Pan African Tsetse and Trypanosomosis Eradication Campaign.

Allele frequencies at four microsatellite loci, and morphometric features based on 11 wing landmarks, were compared among three populations of Glossina palpalis gambiensis (Diptera: Glossinidae) in Guinea. One population originated from the Loos islands separated from the capital Conakry by 5 km of sea, and the two others originated from the continental mangrove area close to Dubreka, these two groups being separated by ≈30 km. Microsatellites and wing geometry data both converged to the idea of a separation of the Loos island population from those of the mangrove area. Although occasional contacts cannot be excluded, our results support the hypothesis of the Loos population of tsetse flies being a completely isolated population. This situation will favor a sequenced intervention against human African trypanosomosis and the possibility of an elimination of tsetse from this island.

Wing geometric morphometry was used to study the spatial structuring of populations of Triatoma infestans from different villages, ecotopes, and sites within a village in northwestern Argentina. A total of 308 male and 197 female wings of T. infestans collected from peridomestic and domestic ecotopes in March 2000 was analyzed. On average, female bugs had a significantly larger wing size than males. Triatomines collected from domiciles or structures associated with chickens had larger wings than bugs collected from goat or pig corrals. The wing size of bugs did not differ significantly between villages. Discriminant analyses of wing shape showed significant divergence between villages, ecotopes, and individual collection sites. The study of metric variation of males between sites belonging to the same ecotope also revealed significant heterogeneity. Indeed, within the same section of the village the difference between two goat corrals was sometimes greater than that between neighboring goat and pig corrals. Thus, morphometric heterogeneity within villages may be the result not only of ecotope and host associations, but also of physical isolation between subunits. The strong structuring of T. infestans populations in the study area indicates that recolonization could be traced back to a small geographic source.

Eight Triatoma dimidiata populations from different geographic regions were compared along with related species using traditional morphometry of head characters. A method for removing allometric change was used for the intraspecific comparisons, and scaling for the isometric change of size was used for the interspecific comparisons. The intraspecific comparison showed significant head shape differences between T. dimidiata populations correlating with geography, showing a separation between the northern, intermediate, and southern collections (more evident in females), and supporting the idea that this species includes several evolutionarily divergent populations. The positioning of one sylvatic group from Guatemala did not correlate with geography, because it was more closely related to a distinct population of Colombia. This sylvatic group was found in caves, while the Colombian specimens, although collected in houses, may have migrated from nearby caves. Evolutionary and/or ecological influences could be responsible for the head shape similarities between these two groups: a common ancestral origin of both populations or a morphological convergence caused by similar environmental pressures. The interspecific comparisons included four other regional species of the same genus, three of them belonging to the phyllosoma complex (T. pallidipennis, T. mexicana, and T. ryckmani, the latter provisionally) and the fourth one classified in the protracta complex (T. nitida). Both complexes were readily separated by their head dimensions, even after size adjustment, and our data support inclusion of T. dimidiata within the phyllosoma complex.

Antennal sensilla patterns were used to explore intraspecific variability among Triatoma infestans (Klug) from domestic habitats in Argentina and Bolivia, and from sylvatic habitats in Bolivia. The sensilla pattern was effective in distinguishing individuals at sexual, ecotopic, and geographic levels, and supported the idea of a lack of gene flow between sylvatic and domestic habitats.

The population genetic structure of Triatoma infestans (Klug), the principal vector of the causative agent of Chagas disease in Bolivia, was investigated by enzyme electrophoresis at 15 loci, of which 3 were polymorphic. A total of 1,286 adults and nymphs was collected from 19 localities of the Cochabamba (high endemicity) and La Paz (low endemicity) departments. Previous results were confirmed, including a low level of polymorphism (0.20), low genetic distance between geographic areas, and a population structure compatible with an isolation by distance model. However, a high proportion (26.3%) of the surveyed localities showed a significant excess of homozygotes, disputing previous conclusions that considered the village as the probable panmictic unit. The excess of homozygotes was reduced when smaller subunits, such as individual houses or chicken coops, were considered, indicating a Wahlund effect.